Method of selective chemical mechanical polishing cobalt, zirconium oxide, poly-silicon and silicon dioxide films.

ABSTRACT

A process for chemical mechanical polishing a substrate containing cobalt, zirconium oxide, poly-silicon and silicon dioxide, wherein the cobalt, zirconium, and poly-silicon removal rates are selective over silicon dioxide. The chemical mechanical polishing composition includes water, a benzyltrialkyl quaternary ammonium compound, cobalt chelating agent, corrosion inhibitor, colloidal silica abrasive, optionally a biocide and optionally a pH adjusting agent, and a pH greater than 7, and the chemical mechanical polishing compositions are free of oxidizing agents.

FIELD OF THE INVENTION

The present invention is directed to a method of selective chemicalmechanical polishing cobalt, zirconium oxide, poly-silicon and silicondioxide films with a chemical mechanical polishing compositioncontaining water, a benzyltrialkyl quaternary ammonium compound, cobaltchelating agent, corrosion inhibitor, colloidal silica abrasive,optionally a biocide and optionally a pH adjusting agent, and a pHgreater than 7, and the chemical mechanical polishing composition isfree of oxidizing agents. More specifically, the present invention isdirected to a method of selective chemical polishing cobalt, zirconiumoxide, poly-silicon and silicon dioxide films with a chemical mechanicalpolishing composition containing water, a benzyltrialkyl quaternaryammonium compound, cobalt chelating agent, corrosion inhibitor,colloidal silica abrasive, optionally a biocide and optionally a pHadjusting agent, and a pH greater than 7, and the chemical mechanicalpolishing composition is free of oxidizing agents, wherein the cobalt,zirconium oxide, and poly-silicon removal rates are selective oversilicon dioxide.

BACKGROUND OF THE INVENTION

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials maybe deposited by several deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Planarization isuseful in removing undesired surface topography and surface defects,such as rough surfaces, agglomerated materials, crystal lattice damage,scratches, and contaminated layers or materials.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates, such assemiconductor wafers. In conventional CMP, a wafer is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thewafer, pressing it against the polishing pad. The pad is moved (e.g.,rotated) relative to the wafer by an external driving force.Simultaneously therewith, a polishing composition (“slurry”) or otherpolishing solution is provided between the wafer and the polishing pad.Thus, the wafer surface is polished and made planar by the chemical andmechanical action of the pad surface and slurry. However, there is agreat deal of complexity involved in CMP. Each type of material requiresa unique polishing composition, a properly designed polishing pad,optimized process settings for both polish and post-CMP clean and otherfactors that must be individually tailored to the application ofpolishing a given material.

In advanced logic nodes ≤10 nm, cobalt metal has replaced tungsten plugconnecting the transistor gates to Back End of Line (BEOL) and the firstfew metal layers (M1 and M2—first and second interconnect metal layersin BEOL of a silicon chip) of copper interconnect metal in BEOL.Advanced logic node manufacturers (≤7 nm) are exploring new high-kdielectric films such as zirconium oxide in combination with cobalt,poly-silicon and silicon dioxide (Tetraethyl orthosilicate oxide) films.To enable the complex integration schemes comprising the above-mentionedfilms, it is desirable to demonstrate CMP slurry that can polish filmswith tunable removal rates and selectivity.

Therefore, there is a need for a CMP polishing method and compositionfor selectively polishing cobalt, zirconium oxide and poly-silicon oversilicon dioxide.

SUMMARY OF THE INVENTION

The present invention provides a method of chemical mechanical polishingcomprising: providing a substrate comprising cobalt, zirconium oxide,poly-silicon and silicon dioxide; providing a chemical mechanicalpolishing composition, comprising, as initial components: water, acolloidal silica abrasive, a cobalt chelating agent, a corrosioninhibitor, a benzyltrialkyl quaternary ammonium compound having aformula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, and, optionally, a biocide; optionally, a pH adjusting agent, anda pH greater than 7, and the chemical mechanical polishing compositionsis free of oxidizing agents; providing a chemical mechanical polishingpad, having a polishing surface; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the polishing surface of the chemical mechanical polishing pad ator near the interface between the chemical mechanical polishing pad andthe substrate; wherein some of the cobalt, zirconium oxide, poly-siliconand silicon dioxide is polished away from the substrate.

The present invention further provides a method of chemical mechanicalpolishing comprising: providing a substrate comprising cobalt, zirconiumoxide, poly-silicon and silicon dioxide; providing a chemical mechanicalpolishing composition, comprising, as initial components: water, acolloidal silica abrasive having a negative zeta potential, a cobaltchelating agent, a corrosion inhibitor; a benzyltrialkyl quaternaryammonium compound having a formula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, and, optionally, a biocide; optionally, a pH adjusting agent, anda pH greater than 7, and the chemical mechanical polishing compositionis free of oxidizing agents; providing a chemical mechanical polishingpad, having a polishing surface; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the polishing surface of the chemical mechanical polishing pad ator near the interface between the chemical mechanical polishing pad andthe substrate; wherein some of the cobalt, zirconium oxide, poly-siliconand silicon dioxide is polished away from the substrate.

The present invention further provides a method of chemical mechanicalpolishing comprising: providing a substrate comprising cobalt, zirconiumoxide, poly-silicon and silicon dioxide; providing a chemical mechanicalpolishing composition, comprising, as initial components: water, acolloidal silica abrasive having a negative zeta potential, a cobaltchelating agent chosen from one or more amino acids, a corrosioninhibitor chosen from one or more heterocyclic nitrogen compound andnonaromatic polycarboxylic acids, a benzyltrialkyl quaternary ammoniumcompound having a formula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, and, a biocide; optionally, a pH adjusting agent, and a pHgreater than 7, and the chemical mechanical polishing composition isfree of oxidizing agents; providing a chemical mechanical polishing pad,having a polishing surface; creating dynamic contact at an interfacebetween the chemical mechanical polishing pad and the substrate; anddispensing the chemical mechanical polishing composition onto thepolishing surface of the chemical mechanical polishing pad at or nearthe interface between the chemical mechanical polishing pad and thesubstrate; wherein some of the cobalt, zirconium oxide, poly-silicon andsilicon dioxide is polished away from the substrate.

The foregoing methods of the present invention include a chemicalmechanical polishing composition comprising, as initial components,water, a colloidal silica abrasive, a cobalt chelating agent, acorrosion inhibitor, a benzyltrialkyl quaternary ammonium compoundhaving a formula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, and, optionally, a biocide; optionally, a pH adjusting agent, anda pH greater than 7, and the chemical mechanical polishing compositionis free of oxidizing agents, wherein polishing cobalt, zirconium oxideand poly-silicon is selective over silicon dioxide.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations havethe following meanings, unless the context indicates otherwise: °C.=degrees Centigrade; g=grams; L=liters; mL=milliliters; μ=μm=microns;kPa=kilopascal; Å=angstroms; mV=millivolts; DI=deionized;mm=millimeters; cm=centimeter; min=minute; sec=second; rpm=revolutionsper minute; lbs=pounds; kg=kilograms; Co=cobalt; ZrOx, wherein x=1 to2=zirconium oxide; BTMAH=benzyltrimethyl ammonium hydroxide;TBAH=tetrabutyl ammonium hydroxide; H₂O₂=hydrogen peroxide;KOH=potassium hydroxide; wt %=weight percent; PVD=physical vapordeposited; RR=removal rate; PS=polishing slurry; and CS=control slurry.

The term “chemical mechanical polishing” or “CMP” refers to a processwhere a substrate is polished by means of chemical and mechanical forcesalone and is distinguished from electrochemical-mechanical polishing(ECMP) where an electric bias is applied to the substrate. The term“poly-silicon” means polycrystalline silicon also called poly-Si a highpurity, polycrystalline form of silicon which consists of small crystalsor crystallites ≤1 mm and is distinct from monocrystalline silicon andamorphous silicon. The term “amino acid” means an organic compoundcontaining amine (—NH₂) and carboxyl (—COOH) functional groups alonewith a side chain (R group) specific to each amino acid. The term “TEOS”means the silicon dioxide formed from the decomposition of tetraethylorthosilicate (Si(OC₂H₅)₄). The term “high-k” dielectric means thematerial, such as zirconium oxide, has a dielectric constant greaterthan silicon dioxide. The terms “a” and “an” refer to both the singularand the plural. All percentages are by weight, unless otherwise noted.All numerical ranges are inclusive and combinable in any order, exceptwhere it is logical that such numerical ranges are constrained to add upto 100%.

The method of polishing a substrate of the present invention, whereinthe substrate includes cobalt, zirconium oxide, poly-silicon and silicondioxide includes a chemical mechanical polishing composition whichcontains (preferably consists of), as initial components, water, acolloidal silica abrasive, a cobalt chelating agent, a corrosioninhibitor, a benzyltrialkyl quaternary ammonium compound having aformula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, wherein the anion is hydroxide, halide, nitrate, carbonate,sulfate, phosphate or acetate, and, optionally, a biocide; optionally adefoaming agent; optionally, a pH adjusting agent, and a pH greater than7, and the chemical mechanical polishing composition is free ofoxidizing agents to provide for the removal of at least some of thecobalt, zirconium oxide, poly-silicon and silicon dioxide from thesubstrate surface to provide cobalt, zirconium oxide and poly-siliconremoval rate selectivity to silicon dioxide.

Preferably, in the method of polishing a substrate of the presentinvention, the water contained, as an initial component, in the chemicalmechanical polishing composition provided is at least one of deionizedand distilled to limit incidental impurities.

The chemical mechanical polishing composition used in the chemicalmechanical polishing method of the present invention preferablycontains, as an initial component, 0.01 to 5 wt % of a benzyltrialkylquaternary ammonium compound having formula (I):

wherein R¹, R² and R³ are each independently chosen from a (C₁-C₄)alkygroup, preferably, a (C₁-C₂)alkyl group, most preferably a methyl group;and wherein the anion is a counter anion to neutralize the positive (+)charge of the benzyltrialkyl quaternary ammonium cation, wherein theanion is hydroxide, halide, nitrate, carbonate, sulfate, phosphate oracetate, preferably, the anion is hydroxide or a halide, such aschloride, bromide, fluoride or iodide. Preferably, the halide ischloride or bromide. Most preferably, the halide is chloride. Thechemical mechanical polishing composition of the present invention alsocontains, as an initial component, 0.1 to 3 wt %, more preferably 0.1 to2 wt %, most preferably 0.2 to 1 wt % of the benzyltrialkyl quaternaryammonium compound having formula (I). Preferably, thebenzyltrialkylammonium compound having formula (I) isbenzyltrimethylammonium hydroxide or benzyltrimethylammonium chloride.Most preferably, the benzyltrialkylammonium compound having formula (I)is benzyltrimethylammonium hydroxide.

In the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided is free oxidizingagents. Oxidizing agents within the scope of the present invention arecompounds utilized to form soft metal oxides that can be polished fasterwhen compared to harder metal surfaces in the presence of appropriateslurry chemistry and pH. Such oxidizing agents which are excluded fromthe chemical mechanical polishing composition of the present inventioninclude, but are not limited to, hydrogen peroxide (H₂O₂),monopersulfates, iodates, magnesium perphthalate, peracetic acid andother per-acids, persulfate, bromates, perbromate, persulfate, peraceticacid, periodate, nitrates, iron salts, cerium salts, Mn (III), Mn (IV)and Mn (VI) salts, silver salts, copper salts, chromium salts, cobaltsalts, halogens, hypochlorites and a mixture thereof. Preferably thechemical mechanical polishing composition of the present invention isfree of hydrogen peroxide, perchlorate, perbromate; periodate,persulfate, peracetic acid or mixtures thereof. Most preferably, thechemical mechanical polishing composition is free of the oxidizing agenthydrogen peroxide.

In the method of chemical mechanical polishing a substrate of thepresent invention, the chemical mechanical polishing compositionincludes colloidal silica abrasive particles. Preferably, in the methodof polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains a colloidal silicaabrasive having a particle diameter of 200 nm or less and a negativezeta potential. More preferably, in the method of polishing a substrateof the present invention, the chemical mechanical polishing compositionprovided contains a colloidal silica abrasive having an average particlediameter of 200 nm or less and a permanent negative zeta potential,wherein the chemical mechanical polishing composition has a pH ofgreater than 7, preferably, from 8 to 13; more preferably, of 8.5 to 11;still more preferably, from 9 to 11; and most preferably 9 to 10.5.Still more preferably, in the method of polishing a substrate of thepresent invention, the chemical mechanical polishing compositionprovided contains a colloidal silica abrasive having an average particlediameter of 200 nm or less and a permanent negative zeta potential,wherein the chemical mechanical polishing composition has a pH ofgreater than 7, preferably, from 8 to 13; more preferably, of 8.5 to 11;still more preferably, of 9 to 11; and most preferably from 9 to 10.5,wherein a zeta potential is from −0.1 mV to −40 mV, preferably, from −10mV to −38 mV, more preferably from −20 mV to −36 mV.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains, as an initial component, a colloidal silica abrasive having anaverage particle diameter of 200 nm or less, preferably, 5 nm to 200 nm;more preferably, 5 nm to less than 200 nm; even more preferably from 10nm to 175 nm, still more preferably from 10 nm to 150 nm, mostpreferably, 20 nm to 100 nm, as measured by dynamic light scatteringtechniques or disk centrifuge method. Suitable particle size measuringinstruments are available from, for example, Malvern Instruments(Malvern, UK) or CPS Instruments (Prairieville, La., USA).

Examples of commercially available colloidal silica particles are FusoPL-3 or SH-3 (average particle diameter of 55 nm) available from FusoChemical Co., LTD.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition providedcontains 0.01 wt % to 10 wt %, preferably 0.05 wt % to 5 wt %, morepreferably, 0.1 wt % to 5 wt %, even more preferably, from 0.2 wt % to 5wt %, and most preferably, from 1 wt % to 5 wt % of a colloidal silicaabrasive having a particle diameter of less than or equal to 200 nm,preferably, 5 nm to 200 nm; more preferably, 5 nm to less than 175 nm;even more preferably from 10 nm to 150 nm, still more preferably from 20nm to 150 nm, most preferably, 20 nm to 100 nm, as measured by dynamiclight scattering techniques. Preferably the colloidal silica abrasivehas a negative zeta potential.

In the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided contains, as aninitial component, a corrosion inhibitor, wherein the corrosioninhibitor is selected from the group consisting of a heterocyclicnitrogen compound, a nonaromatic polycarboxylic acid, and mixturesthereof, wherein the heterocyclic nitrogen compound is selected from thegroup consisting of adenine, 1,2,4-triazole, imidazole, benzotriazole,polyimidazole and mixtures thereof; and, wherein the nonaromaticpolycarboxylic acid includes, but is not limited to oxalic acid,succinic acid, adipic acid, maleic acid, malic acid, glutaric acid,citric acid, salts thereof or mixtures thereof. Preferably, the salts ofthe foregoing nonaromatic polycarboxylic acids are chosen from one ormore of sodium, potassium and ammonium salts. When the chemicalmechanical polishing composition includes a heterocyclic nitrogencompound in the method of chemical mechanical polishing a substrate ofthe present invention, preferably, as an initial component, theheterocyclic nitrogen compound is adenine. When the chemical mechanicalpolishing composition includes a nonaromatic polycarboxylic acid in themethod of polishing a substrate of the present invention, the chemicalmechanical polishing composition provided contains, as an initialcomponent, preferably, the nonaromatic polycarboxylic acid is selectedfrom the group consisting of malic acid, oxalic acid, adipic acid,citric acid, salts thereof and mixtures thereof. More preferably whenthe chemical mechanical polishing composition provided contains, as aninitial component, a nonaromatic polycarboxylic acid, the nonaromaticpolycarboxylic acid is selected from the group consisting of malic acid,citric acid, adipic acid, salts thereof and mixtures thereof. Mostpreferably, in the method of polishing a substrate of the presentinvention, when the chemical mechanical polishing composition providedcontains, as an initial component, a nonaromatic polycarboxylic acid,the nonaromatic polycarboxylic acid is the nonaromatic dicarboxylic acidadipic acid or salts thereof, wherein, preferably, the salts areselected from the group consisting of sodium adipate, potassium adipateand ammonium adipate.

Corrosion inhibitors are included in the chemical mechanical polishingcomposition contain, as an initial component, 0.001 wt % to 1 wt %, morepreferably, from 0.001 wt % to 0.05 wt %, even more preferably from0.005 wt % to 0.01 wt % of a corrosion inhibitor selected from the groupconsisting of a heterocyclic nitrogen compound, a nonaromaticpolycarboxylic acid and mixtures thereof, wherein the heterocyclicnitrogen compounds are selected from the group consisting of adenine,1,2,4-triazole, imidazole, polyimidazole and mixtures thereof; and,wherein the nonaromatic polycarboxylic acid is selected from the groupconsisting of oxalic acid, succinic acid, adipic acid, maleic acid,malic acid, glutaric acid, citric acid, salts thereof and mixturesthereof. Preferably, in the method of polishing a substrate of thepresent invention, the chemical mechanical polishing compositionprovided contains, as an initial component, 0.001 to 1 wt %, morepreferably, 0.001 to 0.05 wt %, most preferably, 0.005 wt % to 0.01 wt%, of the heterocyclic nitrogen compound adenine.

In the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided contains, as aninitial component, a cobalt chelating agent. Preferably, the cobaltchelating agents are amino acids. Such amino acids include, but are notlimited to, alanine, arginine, aspartic acid, cysteine, glutamine,glutamic acid, glycine, histidine, isoleucine, leucine, lysinemethionine, phenylalanine, proline, serine, threonine, tryptophan,tyrosine, valine and mixtures thereof. Preferably, the amino acids areselected from the group consisting of alanine, arginine, glutamine,glycine, leucine, lysine, serine and mixtures thereof, more preferably,the amino acids are selected from the group consisting of alanine,glutamine, glycine, lysine, serine and mixtures thereof, even morepreferably, the amino acids are selected from the group consisting ofalanine, glycine, serine and mixtures thereof, most preferably, theamino acid is glycine.

Chelating agents are included in the chemical mechanical polishingcomposition, as an initial component, from 0.001 wt % to 1 wt %, morepreferably, from 0.05 wt % to 0.5 wt %, even more preferably, from 0.05wt % to 0.1 wt %, most preferably from, 0.025 wt % to 0.1 wt %.

In the method of polishing a substrate of the present invention, thechemical mechanical polishing composition provided has a pH of greaterthan 7. Preferably, in the method of polishing a substrate of thepresent invention, the chemical mechanical polishing compositionprovided has a pH of 8 to 13. More preferably, in the method ofpolishing a substrate of the present invention, the chemical mechanicalpolishing composition provided has a pH of 8.5 to 11; even morepreferably from 9 to 11; and most preferably, in the method of polishinga substrate of the present invention, the chemical mechanical polishingcomposition provided has a pH of 9 to 10.5.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided,optionally, contains a pH adjusting agent. Preferably, the pH adjustingagent is selected from the group consisting of inorganic and organic pHadjusting agents. Preferably, the pH adjusting agent is selected fromthe group consisting of inorganic acids and inorganic bases. Morepreferably, the pH adjusting agent is selected from the group consistingof nitric acid and potassium hydroxide. Most preferably, the pHadjusting agent is potassium hydroxide.

Optionally, in the method of the present invention, the chemicalmechanical polishing composition contains biocides, such as KORDEK™ MLX(9.5-9.9% methyl-4-isothiazolin-3-one, 89.1-89.5% water and ≤1.0%related reaction product) or KATHON™ CG/ICP II containing activeingredients of 2-methyl-4-isothiazolin-3-one and5-chloro-2-methyl-4-isothiazolin-3-one, each manufactured by DuPont deNemours Company, (KATHON and KORDEK are trademarks of DuPont).

In the method of polishing a substrate of the present invention,optionally, the chemical mechanical polishing composition provided cancontain, as an initial component, 0.001 wt % to 0.1 wt %, preferably,0.001 wt % to 0.05 wt %, more preferably, 0.01 wt % to 0.05 wt %, stillmore preferably, 0.01 wt % to 0.025 wt %, of biocide.

Optionally, in the method of the present invention, the chemicalmechanical polishing composition can further include defoaming agents,such as non-ionic surfactants including esters, ethylene oxides,alcohols, ethoxylate, silicon compounds, fluorine compounds, ethers,glycosides and their derivatives. Anionic ether sulfates such as sodiumlauryl either sulfate (SLES) as well as the potassium and ammoniumsalts. The surfactant can also be an amphoteric surfactant.

In the method of polishing a substrate of the present invention,optionally, the chemical mechanical polishing composition provided cancontain, as an initial component, 0.001 wt % to 0.1 wt %, preferably,0.001 wt % to 0.05 wt %, more preferably, 0.01 wt % to 0.05 wt %, stillmore preferably, 0.01 wt % to 0.025 wt %, of a defoaming agent.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing pad provided can be anysuitable polishing pad known in the art. One of ordinary skill in theart knows to select an appropriate chemical mechanical polishing pad foruse in the method of the present invention. More preferably, in themethod of polishing a substrate of the present invention, the chemicalmechanical polishing pad provided is selected from woven and non-wovenpolishing pads. Still more preferably, in the method of polishing asubstrate of the present invention, the chemical mechanical polishingpad provided comprises a polyurethane polishing layer. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing pad provided comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad. Preferably, the chemicalmechanical polishing pad provided has at least one groove on thepolishing surface.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided isdispensed onto a polishing surface of the chemical mechanical polishingpad provided at or near an interface between the chemical mechanicalpolishing pad and the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, dynamic contact is created at the interface between thechemical mechanical polishing pad provided and the substrate with a downforce of 0.69 to 20.7 kPa normal to a surface of the substrate beingpolished.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided has acobalt removal rate ≥900 Å/min; more preferably, ≥950 Å/min; furtherpreferably, ≥960 Å/min; a ZrOx removal rate of ≥80 Å/min; morepreferably, ≥100 Å/min; further preferably, ≥200 Å/min; a Poly-Siremoval rate of ≥1200 Å/min, more preferably, ≥1400 Å/min, furtherpreferably, ≥1500 Å/min; and, preferably, a Co:TEOS selectivity of ≥20,more preferably a Co:TEOS selectivity of ≥60:1; further preferably, aCo:TEOS selectivity of ≥70; preferably, a ZrOx:TEOS selectivity of ≥4:1;more preferably, a ZrOx:TEOS selectivity of ≥10:1; further preferably, aZrOx:TEOS selectivity of ≥13:1; and, preferably, a Poly-Si:TEOSselectivity of 30:1, more preferably, a Poly-Si: TEOS selectivity of≥100:1; and, with a platen speed of 120 revolutions per minute, acarrier speed of 117 revolutions per minute, a chemical mechanicalpolishing composition flow rate of 100 mL/min, a nominal down force of20.7 kPa using 26 mm square coupon wafers on a Bruker Tribolab CMPpolishing machine; and, wherein the chemical mechanical polishing padcomprises a polyurethane polishing layer containing polymeric hollowcore microparticles and a polyurethane impregnated non-woven subpad.

The following examples are intended to illustrate the present inventionbut are not intended to limit its scope.

Example 1 Slurry Formulations

All the slurries in Table 1 used for polishing studies were prepared asmentioned in the following procedure. Glycine and adenine were added tode-ionized water and mixed using an overhead stirrer (300-450 RPM) untilcompletely dissolved to make a final glycine concentration of 0.1 wt %and a final adenine concentration of 0.01 wt %, followed by pHadjustment to pH of 10.3 with dilute KOH solution (5% or 45%). Thecolloidal silica particles were obtained from Fuso chemical Co., LTD:Fuso SH-3 (55 nm average diameter cocoon shaped colloidal silicaparticles forming conjoined spheres having an average length of 70 nm,34 wt % solids as received). The KORDEK™ MLX biocide was then added tothe slurry followed by adding TBAH or BTMAH in the amounts shown inTable 1. Cleanroom grade H₂O₂ (30% solution) was added with stirring toachieve 0.3 wt % H₂O₂ concentration in the final slurry. The slurrieswere used on the same day or the day after H₂O₂ addition in thepolishing experiments.

TABLE 1 Slurry Formulations Tetrabutyl Benzyltrimethyl ammonium ammoniumHydroxide hydroxide KORDEK ™ Glycine Adenine (TBAH) (BTMAH) MLX SH-3H₂O₂ Slurry (wt %) (wt %) (wt %) (wt %) (wt %) (wt %) pH (wt %) CS 1 0.10.01 0.005 5.0 10.3 0 CS 2 0.1 0.01 0.25 0.005 5.0 10.3 0 CS 3 0.1 0.010.50 0.005 5.0 10.3 0 CS 4 0.1 0.01 0.75 0.005 5.0 10.3 0 CS 5 0.1 0.011.00 0.005 5.0 10.3 0 CS 6 0.1 0.01 0.005 5.0 10.3 0.3 CS 7 0.1 0.010.25 0.005 5.0 10.3 0.3 CS 8 0.1 0.01 0.50 0.005 5.0 10.3 0.3 CS 9 0.10.01 1.00 0.005 5.0 10.3 0.3 PS 1 0.1 0.01 0.25 0.005 5.0 10.3 0 PS 20.1 0.01 0.50 0.005 5.0 10.3 0 PS 3 0.1 0.01 0.75 0.005 5.0 10.3 0 PS 40.1 0.01 1.00 0.005 5.0 10.3 0

Example 2 Polishing Experiments

The following cobalt, zirconium oxide, poly-silicon and silicon dioxidepolishing experiments were performed with the slurries disclosed inTable 1 in Example 1 above.

TABLE 2 CMP Polishing and Cleaning Conditions Polishing Tool BrukerTRIBOLAB CMP System Pad VISIONPAD ™ 6000 D37AR--a polyurethane; Shore Dhardness of 57, 30 and 60 μm average diameter closed cell pores andcircular grooves having a depth, width and pitch of 760, 510 and 3,050μm, respectively Conditioner AK45 Ex-Situ-170 μm diamond size; 40 μmdiamond protrusion and 310 μm diamond spacing Process 3 PSI (20.7 kPa),120/117 RPM, 100 mL/min (Downforce, Platen Speed/Carrier Speed, SlurryFlow Rate) Post CMP DI Water clean Polish Time Co Wafer: 20 sec, ZrOx:30 sec, Poly-Si: 10 sec and TEOS Wafer: 60 sec (polishing times were setdifferent for Co, ZrOx, Poly-Si and TEOS due to the differences in theirremoval rates and film thickness and the need to have sufficient Co filmremaining to measure the removal rates accurately).

Cobalt film thickness was measured with OMNIMAP™ RS200 and zirconiumoxide, poly Si, and TEOS film thickness were measured with Asset F5xmeasurement tool both by KLA Corporation. Polishing results are in Table3 below.

TABLE 3 Removal Rate (Å/min) and Selectivity Poly- Poly- Slurry CobaltSi ZrO_(x) TEOS Co:TEOS Si:TEOS ZrO_(x):TEOS CS 1 1007 1544 184 326 3.14.7 0.6 CS 2 958 1587 193 297 3.2 5.3 0.6 CS 3 931 1280 165 213 4.4 6.00.8 CS 4 991 1494 173 204 4.9 7.3 0.8 CS 5 929 1438 143 127 7.3 11.3 1.1CS 6 136 2058 140 283 0.5 0.5 7.3 CS 7 89 288 85 60 1.5 1.4 4.8 CS 8 73101 59 23 3.1 2.5 4.3 CS 9 0 27 30 8 0.0 3.8 3.4 PS 1 979 1604 221 4820.5 33.6 4.6 PS 2 967 1584 206 15 64.6 105.8 13.8 PS 3 963 1408 143 1470.3 102.8 10.5 PS 4 968 1250 83 11 84.7 109.3 7.3

Example 3 Static Etch Rate (Corrosion) Analysis

Blanket Co wafers from Novati Technologies (200 mm, ˜1700 Å thick PVD Codeposited on to silicon substrate) were used as received. Gamry PTC1™paint test cells were used for analysis, the whole 200 mm Co wafer wasclamped between a glass tube with an O-ring seal and a custom-madeTEFLON™ base. 3M-470, electroplaters tape with 3.0 cm² of open area wasused in-between the wafer and the O-ring to avoid any crevice or stresstype local corrosion. For high temperature analysis, 30 mL ofstatic-etch slurry was kept in an oven at 55° C. to simulate higherlocal temperatures at pad asperity/wafer contact during polishing, andpre-heated for 60 min and then the slurry was immediately added to thestatic-etch cell and kept in contact with the wafer for 3 min. After thedesired hold time, the static-etch solution was collected and analyzedfor Co ions by Inductively Coupled Plasma—Optical Emission Spectrometer(ICP-OES) analysis after centrifuging and separating the colloidalsilica abrasives when present in the formulation. Colloidal silicaabrasives were excluded from some formulations in static-etchexperiments for ease of ICP-OES analysis. At least two data points werecollected for all the slurries tested to check for reproducibility.

Cobalt static-etch rates (SER) were calculated from cobalt concentrationin ICP analysis using the following formula:

Cobalt SER (Å/min)={[C (g/L)*V (l)]/[A (cm²)*D (g/cm³)*T(min)]}*10^({circumflex over ( )}8)

C=Co concentration from ICP analysis (g/l)

V=Volume of test solution used added in static etch setup (l)

A=Area of cobalt metal exposed to the test solution (cm²)

D=Density of cobalt (8.9 g/cm³)

T=Time of exposure (min)

10^({circumflex over ( )}8)=cm to Å unit conversion

TABLE 4 55° C. Static-etch Rate (Å/min) Slurry Cobalt CS 1 <1.5 CS 2<1.5 CS 3 <1.5 CS 4 <1.5 CS 5 <1.5 CS 6 2.1 CS 7 1.7 CS 8 1.8 CS 9 2.0PS 1 <1.5 PS 2 <1.5 PS 3 <1.5 PS 4 <1.5

What is claimed is:
 1. A method of chemical mechanical polishing method,comprising: providing a substrate comprising cobalt, zirconium oxide,poly-silicon and silicon dioxide; providing a chemical mechanicalpolishing composition, comprising, as initial components: water, acolloidal silica abrasive, a cobalt chelating agent, a corrosioninhibitor, a benzyltrialkyl quaternary ammonium compound having aformula:

wherein R¹, R² and R³ are each independently selected from a (C₁-C₄)alkygroup, and, optionally, a biocide; optionally, a pH adjusting agent, anda pH greater than 7, and the chemical mechanical polishing compositionsis free of oxidizing agents; providing a chemical mechanical polishingpad, having a polishing surface; creating dynamic contact at aninterface between the chemical mechanical polishing pad and thesubstrate; and dispensing the chemical mechanical polishing compositiononto the polishing surface of the chemical mechanical polishing pad ator near the interface between the chemical mechanical polishing pad andthe substrate to remove at least some of the cobalt.
 2. The method ofclaim 1, wherein the benzyltrialkyl quaternary ammonium compound is inamounts of 0.1-3 wt %.
 3. The method of claim 1, wherein thebenzyltrialkyl quaternary ammonium compound is selected from the groupconsisting of benzyltrimethylammonium hydroxide, benzyltrimethylammoniumchloride and mixtures thereof.
 4. The method of claim 1, wherein theanion is selected from the group consisting of hydroxide, halide,nitrate, carbonate, sulfate, phosphate and acetate.
 5. The method ofclaim 1, wherein the colloidal silica abrasive has a permanent negativezeta potential.
 6. The method of claim 1, wherein the corrosioninhibitor is a heterocyclic nitrogen compound, an aromaticpolycarboxylic acid or mixtures thereof.
 7. The method of claim 1,wherein the chelating agent is an amino acid.
 8. The method of claim 7,wherein the amino acid is selected from the group consisting of alanine,arginine, aspartic acid, cysteine, glutamine, glutamic acid, glycine,histidine, isoleucine, leucine, lysine methionine, phenylalanine,proline, serine, threonine, tryptophan, tyrosine, valine and mixturesthereof.
 9. The method of claim 1, wherein the pH is from 8-13.